OBJECTIVES: 1. We are examining the functional significance of whole kidney volume/pressure events; specifically we are examining whether the renal swelling which occurs following acute renal injury is the result of an increase in whole kidney compliance, an increase in intrarenal pressure, or both. These studies have relevance to certain important states of renal injury such as acute renal failure following ischemia of the kidney or the acute renal injury which occurs in transplant rejection. In both of these situations marked renal swelling may occur and, as we have previously reported, such swelling per se appears to impair renal function. 2. We have devised a means for examining the fractional uptake of immune complexes by the major organ systems of the body. The technique consists in infusing simultaneously with the immune complexes, radioactive microspheres which act as markers of tissue blood flow. With this technique, we are presently examining the effect of hemodynamic alterations on immune complex trapping and will shortly be examining the effect of pharmacologic agents. With this technique, it is possible to examine specifically those factors which interfere with immune complex trapping even though these factors may also simultaneously affect renal blood flow.